Here you can create your own versions (clients) filter. Click the "Add default filter" button if you want to add the defult filter which allows players to join using all vanilla and all Optifine versions. Along the default filter, you can add your own versions (clients) by clicking the "Add versions (cliens)" button. After you have created your list, click "Download filter" and follow further instructions.
There are no versions currently on the list! Click "Add versions" to add a version.